Effects of different drying methods on physicochemical properties of egg yolk powder

Abstract: spray drying, vacuum freeze drying, hot air drying, infrared drying and microwave drying equipment were used to study the effects of different drying methods on the physicochemical properties of egg yolk powder. The moisture content, thermal stability, color, emulsifying property and powder structure of yolk powder prepared by different drying methods were determined.

The results showed that the moisture content of yolk powder was the lowest (2.5%), and the moisture content of yolk powder was the highest (3.9%). The difference between the two groups was significant (P<0.05). The moisture content of yolk powder from these 5 drying methods was less than 4%, which accords with the current standard of egg products. The color of yolk powder obtained from hot air drying is the worst (brightness is only 83.45). The egg yolk powder obtained by vacuum freeze-drying is the best emulsifying power, while the dried egg yolk powder has the worst emulsifying ability. The powder of egg yolk powder prepared by spray drying is spherical and uniform, and the egg yolk powder produced by the 4 drying methods is massive.

According to the above results, the physical and chemical properties of yolk powder are greatly affected by the drying method. In actual production, different drying methods can be used to produce special yolk powder according to different needs.

Key words: drying method; microwave drying of yolk powder; physicochemical properties; powder structure

Egg yolk is about 28%~29% of egg weight, including egg yolk lecithin, low density lipoprotein, high-density lipoprotein, high vitelloprotein and other bioactive substances. Therefore, egg yolk has high nutritional value and multiple functional properties (such as emulsification, gelation, etc.).

After separating the yolk from the egg white, the yolk powder can be prepared by drying. The yolk powder contains about 30% protein, 38% glyceride and 19% phospholipids. In addition, there are a small amount of sugar, minerals, vitamins, pigments, enzymes and so on. Compared with yolk liquor, yolk powder has the advantages of long shelf life, good functional stability, easy production, transportation and storage. Its uses include extracting lecithin in the pharmaceutical industry, using it in the food industry as mayonnaise, salad dressing, baking food, cold drinks (ice cream, ice cream) and auxiliary materials of full-price nutritional food.

In the production of yolk powder, it is necessary to remove water from yolk liquid to make powder. At present, domestic and foreign scholars mostly focus on the extraction of emulsifying active ingredients in yolk and the modification of yolk. However, in the production of yolk powder, the effects of different drying methods on its physical and chemical properties have not been reported. Therefore, five drying methods commonly used in the production of yolk powder are selected in this study. Drying method (spray drying, vacuum freeze-drying, hot air drying, infrared drying and microwave drying) was used to prepare egg yolk powder. The effects of different drying methods on moisture content, thermal stability, color, emulsification and microstructure of egg yolk powder were studied in order to provide theoretical basis and technical support for the production and processing of yolk powder.